Lubricating grease composition

ABSTRACT

A highly corrosion resistant lubricating grease cmposition comprising a lubricating oil thickened with a gelling agent wherein the lubricating oil is prepared by intimately admixing a synthetic halogen containing polymeric lubricating oil and a fluorocarbon resin, freezing the mixture and thawing the frozen product.

United States Patent [1 1 Chapman Feb. 19, 1974 LUBRICATING GREASECOMPOSITION [75] Inventor: Richard Metthews Chapman, Gales Ferry, Conn.

[73] Assignee: CMR & T, Inc., Westerly, RI.

[22] Filed: June 7, 1972 211 Appl. No.: 260,543

[52] US. Cl 252/28, 117/132 CF, 252/37.2, 252/40.7, 252/42.1, 252/49.6,252/54,

[51] Int. Cl. Cl0m 7/50, ClOm 7/28 [58] Field of Search. 252/28, 37.2,40.7, 42.1, 49.6, 252/54, 58, 389, 396, 388; 117/132 CF [56] ReferencesCited UNITED STATES PATENTS 2,679,479 5/1954 Peterson et al. 252/283,011,975 12/1961 Nitzsche et al. 252/28 3,453,210 7/1969 Wright3,505,229 4/1970 Skehan 252/54 Primary Examiner-Daniel E. WymanAssistant ExaminerI. Vaughn Attorney, Agent, or Firm--Cameron, Kerkam,Sutton, Stowell & Stowell [57] ABSTRACT 14 Claims, N0 Drawings 1LUBRICATING GREASE COMPOSITION BACKGROUND ,OF INVENTION The presentinvention relates to a synthetic lubricating grease composition.

The employment of greases as lubricants in special applications wheredesign simplicity, less need for maintenance and decreased realingrequirements preclude the use of oils is well known. Recently, however,there has been an increasing demand for greases which are capable ofapplication in high temperature environments, i.e., aircraft, militaryequipment, rocketry, etc. The greases based on petroleum oilcompositions are entirely unsuitable in these areas because of theirrelatively low heat resistances.

As a result many grease compositions based on synthetic oils have beensuggested for use in high tempera ture environments. For example, it hasbeen suggested to employ certain polyesters as bases for hightemperature greases. Thus, di(2-ethylhexyl) sebacate and other polyesteroils have been employed to formulate such greases. These polyester basedgreases are only effective, however, at temperatures up to about300350F.

The so-called silicone greases have been suggested for use at highertemperatures. Although the silicones resist temperatures up to as highas 45 OF., their lubric' ity is relatively poor for gears, actuators andother sliding devices. Attempts to overcome this disadvantage byblending the silicones with polyesters have met with only limitedsuccess.

It has also been suggested to employ thickened alkyl biphenyl andpolyphenyl ester oils as greases; however, they have only a limitedrange of uses.

Most recently it has been proposed to formulate high temperature greasesfrom polyand per-halogenated polymer oils. Greases based upon these oilshave an extrcmely high resistance to elevated temperatures and evidenceexcellent lubricity properties. A serious disadvantage associated withthese greases, however, is that it is extremely difficult to avoidcorrosion of the metal parts which come in contact with the grease inthe presence of moisture. Metals which are corroded in the presence ofthese greases include steels, copper and aluminum. The halogenatedgreases are particularly disadvantageous when employed in systemsconstructed of aluminum. Such greases commonly detonate when in contactwith aluminum at high temperatures under conditions of shear.

Heretofore it has been suggested to improve the corrosion properties ofthe poly-halogenated greases by in-corporating various anti-corrosionagents therein. For example, such anti-corrosion agents asamine salts,metal sulfonate and naphthenates, esters, sodium nitrite, and non-ionicsurfactants have been employed to avoid water and salt spray corrosion.

The use of these anti-corrosion agents has more or less met withfailure, however, due in part to a prior lack of understanding as to thereasons for the great susceptibility of metals to corrosion in thepresence of polyhalogenated oils. Indeed, it has recently been foundthat these oils actually promote or catalyze the corrosion of metals inthe presence of moisture. The dilemma facing the prior art in solvingthe problem has reached such proportions that efforts to avoid corrosionhave taken the form of attempts to completely exclude moisture from theenvironments wherein these greases are utilized. As will be apparent tothose skilled in the art, systems contemplating the complete avoidanceof moisture would entail the use of very elaborate and expensivecontrols. Indeed, it would defeat the very advantages associated withthe use of greases, namely, design simplicity, decreased sealingrequirements, maintenance reductions, etc.

An additional disadvantage associated with the use of anti-corrosionagents in these types of greases is that these materials very often tendto inhibit or deleteriously affect the lubricating action of thegreases. Indeed, in some instances, these agents actually promote thedecomposition of the polyhalogenated polymers making up the greases.

Finally, the use of anti-corrosion agents increases the expense involvedin formulating high-temperature greases.

It is an object of the present invention to provide lubricating greasecompositions based on polyhalogenated polymeric oils which avoid andsubstantially completely inhibit the corrosion of metals with which itcomes in contact in the presence of moisture.

It is a further object of the invention to provide a lubricating greasecomposition based on polyhalogenated polymeric oils which isanti-corrosive in the absence of added anti-corrosion agents.

It is still a further object of the invention to provide a lubricatinggrease composition based on polyhalogenated polymeric oils which isanti-corrosive without the necessity for excluding the presence ofmoisture from systems wherein they are employed.

SUMMARY OF THE INVENTION These and other objects of the invention arerealized by the provision of a new lubricating grease compositioncontaining a polyhalogenated polymeric oil prepared according to thehereinafter-described process.

I have found that a lubricating oil which remarkably resists thecorrosion of metals with which it comes in contact in the presence ofmoisture is produced by:

l. intimately admixing a halogenated polymeric oil with a fluorocarbonresin 2. freezing the resulting mixture to a solid state, and

3. thawing the frozen mixture to produce the anticorrosive lubricatingoil composition.

DETAILED DESCRlPTION OF THE INVENTION The invention is predicated on thediscovery that a new and highly anti-corrosive synthetic grease may beformulated from a halogenated polymeric oil prepared from ingredientswhich are themselves relatively highly corrosive to metals in thepresence of moisture by the afore-described method involving intimateadmixture, freezing and thawing.

I am unaware of the mechanism by which this method impartsanti-corrosive properties to the oil composition. Nor am I aware of thephysical or chemical changes which take place in the ingredients of theoil composition to render the latter anti-corrosive. It has been found,however, that the oil and fluorocarbon resin admixture must be subjectedto only one freeze and thaw cycle. If the thawed composition is againfrozen and thawed, whatever corrosion resistant properties were impartedto the composition by the first cycle of freezing and thawing are lost.Care should be taken therefore to avoid refreezing the composition afterthawing.

It is critical to the practice of the invention that the steps of theabove method be carried out in the exact order set forth. Thecomposition produced by merely admixing the oil and resin ingredientswithout freezing is not anti-corrosive. Moreover, merely freezing thevarious ingredients without having first intimately admixed themproduces no change in the anti-corrosive characteristics thereof.Furthermore, the oil and resin must be intimately admixed prior tofreezing. Freezing and thawing the ingredients separately and thenadmixing them does not render the mixture anti-corrosive.

Any of the well-known synthetic halogen containing polymeric oils may beutilized in the practice of the invention. These oils are well known inthe art and generally, although not necessarily, comprise fluorinatedsynthetic polymers having a degree of polymerization sufficient toimpart a relatively high viscosity to the resulting liquid. Although theoils most commonly employed comprise fluorinated polymers, it is to beunderstood that the invention is applicable to any synthetic polymericoil containing fluorine, chlorine, bromine,

iodine or mixtures thereof. Typical among these are the poly-halogenatedvinyl halides, polyhalogenatedethylenes, poly-halogenated silicones,

poly-halogenated ethers, etc. Exemplary of these oils are trifluorovinylchloride polymers, chlorotrifluoroethylene polymers,trifluoroproplymethylpolysilicones, perfluoroalkylpolyethers, etc. It isto be understood that the foregoing examples of suitable oils are notlimitative of the scope of the invention. Any synthetic halogenatedlubricating oil composition may be rendered substantially non-corrosiveto metals in the presence of moisture according to the presentinvention. Obviously, the selection of a particular oil will depend uponthe application intended or the system in which it is to be employed.

The above-described synthetic halogenated oils are well known and may beprepared according to methods similarly well known in the prior art. Forexample, the chlorotrifluoroethylene polymeric oils may be prepared byseparating into fractions of oils, greases and waxes the products of thepolymerization of chlorotrifluoroethylene and then pyrolyzing theproducts to produce a halocarbon oil of low boiling range having arelatively high viscosity and a molecular weight lower than the originalpolymeric product. The oil, grease and wax fractions may be pyrolyzedsingly or in combination. The halogenated polyvinyl, silicone,polyether, etc., oils may also be prepared according to methods wellknown in the prior art.

I have found that the invention is applicable only to the employment ofa fluorocarbon resin. As previously stated, the reasons for the uniquesusceptibility of only this type of material for aiding in theimprovement of the anticorrosive nature of the aforedescribed oils areat present unknown. Suffice it to state that numerous different types ofmaterials have been tested and found unsuitable.

The fluorocarbon resin is most preferably reduced to a finely dividedstate and suspended in a liquid, e.g., a silicone oil, compatible withthe halogenated oil with which it is to be mixed to form a grease-likeproduct. The preferred fluorocarbon resin is polytetrafluoroethylene. Aproduct manufactured under the name Dixon 164 by the Dixon Corporation,Bristol, Rhode Island has been found to be particularly useful.

The highly anti-corrosive properties are imparted to the oil compositionby ultimately admixing from about 3.0 percent to about 5.0 percent,preferably about 4.0 percent, by weight, of the fluorocarbon grease withthe oil, freezing the admixture to a solid state, and thawing the frozenmixture. It is to be understood, however, that the addition of anyamount of the fluorocarbon resin in accordance with the practice of theinvention will result in imparting at least a degree ofanticorrosiveness to the oil.

Any conventional apparatus may be employed for admixing the oil andgrease; it being necessary only that an intimate admixture of the twoingredients be' obtained. If desired, conventional emulsifying agentsmay be added to the ingredients to facilitate mixing.

The intimate admixture is then frozen to the solid state. This may beaccomplished according to any well known freezing method. The mostconvenient and practical method is to place the mixture in a suitablecontainer which is resistant to low temperatures and immerse thecontainer in a cyrogenic fluid such as liquid nitrogen, argon, neon,oxygen, etc. It is to be understood, however, that any system capable ofproducing temperatures sufficiently low to freeze the oil-resinadmixture may be employed to achieve freezing. It is necessary only thatthe mixture be frozen to a substantially completely solid state.

Following freezing, the mixture is thawed and formulated into the greasecomposition. Prior to preparing the grease, however, the pH of themixture should be adjusted to a minimum value of about 5.1.

The lubricating greases of the invention may be prepared by thickeningthe above-described anti-corrosive oil with any suitable gelling agent.

Finely divided silica is the preferred gelling or thickening agent. ltis to be understood, however, that any conventional thickening agent maybe employed.

Exemplary of the gelling agents suitable for use in formulating thegreases of the invention are the fatty acid soaps of lithium, calcium,sodium, aluminum, barium, etc. Suitable fatty acids include oleic,palmitic, stearic and carboxylic acids derived from tallow, hydrogenatedfish oil, castor oil, wool grease, rosin, etc. Additional gelling agentswhich may be utilized are the finely divided bentonite and hectoriteclays which have been surface modified with organic materials such asquaternary ammonium compounds and carbon black.

The greases of the invention may be prepared according to any of thewell known methods for formulating grease compositions. In addition, anyof the well known additives conventionally employed in greasecompositions may be included.

The amount of gelling agent employed is not critical and will dependupon the intended use of the grease. When employing the preferredgelling agent, i.e., finely divided silica it has been found that thepresence of 5 wt. percent of silica in the oil yields a grease having anNLGl (National Lubrication Grease Institute) value, at room temperature,of approximately 0. The presence of 10 wt. percent silica yields anapproximate NLGl value of 1. By increasing the amount of silica inincrements of 5 wt. percent, the NLGl value is increased byapproximately 1 with each addition.

Thus, it will be apparent that a grease having any desired consistencymay be prepared by varying the amount of gelling agent over a widerange. Generally, amounts of gelling agent above 25 wt. percent,dependent upon the nature of the gelling agent, yield solidifed productshaving limited utility as greases.

Any mixing apparatus may be employed to admix the oil and gelling agent.It is only necessary to achieve an intimate and homogenous admixturebetween the oil and gelling agent in order to provide a suitable greasecomposition.

The invention will be further illustrated by reference to the followingnon-limiting specific examples wherein all parts are by weight:

EXAMPLE 1 229 g of a polychlorotrifluoroethylene oil having a pour pointof 50C., a viscosity at 100F. of 34, and initial boiling point of 500F.and a cloud point of 18F. were added along with 9.16 g of apolytetrafluoroethylene resin suspension (Dixon 164 Dixon Corporation,Bristol, Rhode Island) to a commercial household type blender. Themixture was agitated at a blender speed of 19,000 RPM until thecomponents were completely and intimately admixed. The admixture wasthen poured into a container and covered with a securely fitting cap.The container was completely immersed in liquid nitrogen contained in aDeWar vessel for 1 /2 hours until frozen solid.

The container was removed from the liquid nitrogen and allowed to thawundisturbed at room temperature. After thawing, the contents of thecontainer were poured into a homogenizer and homogenized. Thehomogenized mixture was returned to the blender and 0.24 g of linearaural sulfate detergent and 1.2 g of polyisobutylene wetting agent addedthereto. The contents were blended for several minutes to ensurecomplete mixing of the ingredients. The mixture was found to have anaverage pH of 6.7 A sufficient amount of fumed silica (Cabosil ST-l,Cabot Co., Boston, Mass.) was added to one pint of the above oil in astainless steel vessel to yield a product containing wt. percent ofsilica. The mixture was thoroughly hand-stirred with a stainless-steelrod until the silica was completely and intimately admixed with the oil.The resultant grease was found to have an NLGl value of approximately 1.

The grease was employed to lubricate an operating valve in a hot waterline (198-200F). The bronze valve was found to be non-corroded afterextended use. In addition, the grease remained unaffected duringoperation of the valve.

EXAMPLE 2 40.2 g of a polytrifluorovinyl chloride oil having a pourpoint of -40C., a viscosity of 100F. of 35 and initial boiling pointof100C. and 1.6 g. of a polytetrafluorethylene suspension Dixon 164) wereadmixed and processed according to the procedure set forth in Examplel.A sufficient amount of fumed silica (Cabosil ST-l) was added to one pintof the oil to produce a mixture containing wt. percentof silica. Themixture was thoroughly admixed as in example 1 to provide a greasehaving an NLGl value of approximately 2. v

The grease was applied to separate carbon steel and stainless-steelsurfaces and subjected to an atmosphere of hydrogen sulfide for 100hours. The metal surfaces remained non-corroded.

EXAMPLE 3 220 g of trifluoropropylmethylpolysilicone oil having aviscosity of 100F. of 25 and an initial boiling point of 400F. and 8.8 gof a polytetrafluoroethylene suspension (Dixon 164) were admixed andprocessed according to the procedure set forth in Example 1.

A sufficient amount of fumed silica (Cabosil ST-l) was added to one pintof the oil to produce a mixture containing 20 wt. percent of silica. Themixture was thoroughly admixed as in Example 1 to yield a very viscousgrease having an NLGI value of approximately 3.

The grease was cut with wt. percent of Freon and applied to the steelchain linkage of a sprocket type, chain-driven drying kiln with a brush.After evaporation of the freon, the kiln was operated continuously forthree days. Despite exposure to high temperatures and excess moisture,the grease provided a high degree of lubricity while protecting themetal surfaces from corrosion.

EXAMPLE 4 105 g of a perfluoroalkylpolyether oil having a pour point ofC., a viscosity of 100F. of 36 and an initial boiling point of 550" F.and having 4.2 g of a polytetrafluoroethylene suspension (Dixon 164)were admixed and processed as in Example 1.

A sufficient amount of fumed silica (Cabosil ST-l) was added to one pintof the oil to produce a mixture containing 25 wt. percent of silica. Themixture was thoroughly admixed as in Example 1 to yield a very viscousgrease having an NLGI value of slightly less than 4.

In the foregoing examples, Dixon 164 is a percent suspension ofpolytetrafluoroethylene in a silicone oil.

The greases of the present invention have a variety of applications,particularly in those areas wherein the metalic parts contacted by theoils are highly susceptible to corrosion. Exemplary of such systems arethose reactive with conventionally employed petroleum hydrocarbongreases; systems for processing liquid oxygen, hydrogen and other highlyreactive materials; flotation and damping equipment; valves andstopcocks; high pressure systems; heavy duty gear boxes, transmissions;pumping equipment; stationary and mobile hydraulic systems such as thoseutilized on ships and planes, etc.

The grease is particularly suited for use in aluminum componentcontaining systems which normally cause the detonation of conventionallubricants under conditions of high shear. The greases of the presentinvention, on the other hand, are highly resistant to detonation in thepresence of aluminum under shear. Accordingly, they find particularapplication in the aircraft inresin, freezing said mixture to a solidstate and thawing said frozen mixture.

2. The composition of claim 1 wherein said halogen is selected from thegroup consisting of chlorine, fluorine, bromine, iodine and mixturesthereof.

3. The composition of claim 2 wherein said halogen is fluorine.

4. The composition of claim 2 wherein said oil is apolychlorotrifluoroethylene.

5. The composition of claim 2 wherein said oil is a polytrifluorovinylchloride.

6. The composition of claim 2 wherein said oil is atrifluoropropylmethyl polysilicone.

7. The composition of claim 2 wherein said oil is aperfluoroalkylpolyether.

8. The composition of claim 1 wherein said fluorocarbon resin ispolytetrafluoroethylene.

9. The composition of claim 8 wherein said polytetrafluoroethylene is inthe form of a suspension thereof in a liquid silicone miscible with andinert with respect to said oil.

10. The composition of claim 1 wherein said gelling agent is a fattyacid metal soap.

11. The composition of claim 10 wherein said metal is selected from thegroup consisting of lithium, calcium, barium and aluminum.

12. The composition of claim 1 wherein said gelling agent is selectedfrom the group consisting of organic agent surface modified, finelydivided bentonite and hectorite clays.

13. The composition of claim 1 wherein said gelling agent is finelydivided silica.

14. The composition of claim 1 wherein said grease contains up to about25 wt. percent of gelling agent.

2. The composition of claim 1 wherein said halogen is selected from thegroup consisting of chlorine, fluorine, bromine, iodine and mixturesthereof.
 3. The composition of claim 2 wherein said halogen is fluorine.4. The composition of claim 2 wherein said oil is apolychlorotrifluoroethylene.
 5. The composition of claim 2 wherein saidoil is a polytrifluorovinyl chloride.
 6. The composition of claim 2wherein said oil is a trifluoropropylmethyl polysilicone.
 7. Thecomposition of claim 2 wherein said oil is a perfluoroalkylpolyether. 8.The composition of claim 1 wherein said fluorocarbon resin ispolytetrafluoroethylene.
 9. The composition of claim 8 wherein saidpolytetrafluoroethylene is in the form of a suspension thereof in aliquid silicone miscible with and inert with respect to said oil. 10.The composition of claim 1 wherein said gelling agent is a fatty acidmetal soap.
 11. The composition of claim 10 wherein said metal isselected from the group consisting of lithium, calcium, barium andaluminum.
 12. The composition of claim 1 wherein said gelling agent isselected from the group consisting of organic agent surface modified,finely divided bentonite and hectorite clays.
 13. The composition ofclaim 1 wherein said gelling agent is finely divided silica.
 14. Thecomposition of claim 1 wherein said grease contains up to about 25 wt.percent of gelling agent.